Solid phase versus solvent extraction of pesticides from water

The average recovery for 12 pesticides spiked into 100 ml of water at 0.1 ppb was 90% when cartridges containing 100 mg of C-18 bonded porous silica were used for adsorption. Flow rates of up to 200 bed volumes per minute were employed for the adsorption step. Quantitative desorption of the pesticides was accomplished with less than 100l of solvent, thus eliminating the need for a solvent reduction step. The pesticides from samples of surface waters were adsorbed onto C-18 bonded porous silica at the sampling site and the cartridges containing the bonded phase were returned to the laboratory for elution and analysis. The analytical results obtained from use of this procedure agreed with those obtained for duplicate samples of the water that were processed in the laboratory using standard solvent extraction procedures.